The present invention relates to a writing instrument which has a good writing performance even after a pen tip is left standing in the air for a long period of time and which is excellent in a cap-off performance.
Writing instruments in which inks are penetrated into pen tips comprising a fibrous feed or a plastic feed so as to write, such as a marking pen, a sign pen and a brush pen have so far been used in many cases.
However, when a cap is taken away to leave a pen tip part standing in the air for long tome, there is involved the problem that the pen tip part is dried to cause inferior writing.
In the past, writing instruments such as a marking pen, a sign pen and a brush pen each having an excellent cap-off performance are obtained by adding to inks, additives such as higher fatty acid esters of specific polyglycerin, specific acidic phosphoric acid higher alcohol esters and salts thereof, specific phosphorous acid higher alcohol esters and specific decaglycerin stearic acid esters each of which makes it possible to inhibit vaporization (Japanese Patent Publication No. Sho 62-34352 and Japanese Patent Application Laid-Open No. Sho 61-261380).
However, a large part of additives having a high vaporization-inhibiting effect has a solubility of 10% by weight or less in solvents and has a problem in terms of a low solubility. In particular, the solubility at 0xc2x0 C. is 5% by weight or less, and there are the problems that storage at a low temperature and repeating of low and high temperatures produce precipitations of the additives described above in the inks and bring about clogging in the ink passages to reduce the writing property or deteriorate the cap-off property with the passage of time.
On the other hand, disclosed in Japanese Patent Application Laid-Open No. Hei 7-242094 is a dry-preventing method for a writing instrument in which in order to effectively inhibit an ink solvent from volatilizing from a writing part in a period of time passing until first writing after producing the writing instrument to prevent inferior writing in a non-use state from being caused over a long period of time, one end part of a writing feed comprising a porous feed material is inserted into an ink reservoir absorbing an ink prepared by dissolving a dye in solvents and the other end is formed in a writing part of the writing instrument and in which a high boiling solvent such as benzyl alcohol having a slow volatilizing speed among the ink solvents is coated on or impregnated into the writing part of the writing feed described above.
However, the dry-preventing method disclosed in this gazette has an object to prevent drying in a period of time passing until first writing after producing the writing instrument, and a target thereof is a high boiling solvent such as benzyl alcohol having a slow volatilizing speed among the ink solvents, so that the writing part is not prevented from being dried after writing, and it is different from the present invention in terms of an object, an action and a structure (technical idea). Further, benzyl alcohol used for the dry-preventing method for a writing instrument described above is liquid at room temperature and freely miscible with solvents, and it has the problem that if it is left standing over a long period of time, it is introduced into the ink reservoir by diffusion of the solution and the effect is almost lost. Further, benzyl alcohol flows out by writing once, and therefore the effect is not continued to be shown until the ink is exhausted.
Accordingly, the existing state is that in writing instruments such as a marking pen, a sign pen and a brush pen each having a pen tip comprising a fibrous feed or a plastic feed, demanded are writing instruments which have a good preservability at a low temperature and in which a cap-off performance is not deteriorated with the passage of time and that desired are writing instruments which do not bring about starving in writing as well when the pen tip is left standing in the air over a long period of time by forgetting to put the cap and which provides an excellent writing performance.
In light of the problems on the conventional techniques described above, the present invention intends to solve them, and an object thereof is to provide a writing instrument which has a good preservability at a low temperature and does not cause clogging in an ink passage and which provides a good writing performance even after the pen tip is left standing in the air over a long period of time and is excellent in a cap-off performance.
Intensive investigations of the problems of the conventional techniques described above repeated by the present inventors have resulted in finding that in order to obtain writing instruments such as a marking pen, a sign pen and a brush pen each having an excellent cap-off performance, pen tips comprising a fibrous feed or a plastic feed which are used for these writing instruments are coated with an additive which is less liable to be dissolved in solvents and has a vaporization-inhibiting effect, whereby a writing instrument meeting the object described above can be obtained. Thus, they have come to complete the present invention.
That is, the writing instrument of the present invention having an excellent cap-off performance comprises the following items (1) to (8).
(1) A writing instrument having an excellent cap-off performance, wherein in the writing instrument having a pen tip comprising a fibrous feed or a plastic feed, the pen tip described above is coated with a substance which is solid at room temperature and in which a solubility in an ink solvent is 10% or less at room temperature and which repeatedly and constantly films on a surface part of the pen tip that can be broken by writing pressure in writing, among substances providing the pen tip with a cap-off property.
(2) The writing instrument having an excellent cap-off performance as described in the above item (1), wherein the coated substance has a melting point of 40 to 95xc2x0 C.
(3) The writing instrument having an excellent cap-off performance as described in the above item (1) or (2), wherein the coating substance is at least one selected from glycerin derivatives, alkylphosphoric acid esters, polyoxyethylenesorbitan fatty acid esters, polyoxyethylenesorbit fatty acid esters, paraffin wax, microcrystalline wax, polyolefin wax, pentaerythritol derivatives and lecithin.
(4) The writing instrument having an excellent cap-off performance as described in any of the above items (1) to (3), wherein the amount coated on the pen tip is 0.01 to 20% by weight in terms of a weight ratio.
(5) The writing instrument having an excellent cap-off performance as described in any of the above items (1) to (4), wherein a substance which is solid at room temperature and in which a solubility in an ink solvent is 0.01 to 10% at room temperature among substances providing a cap-off property being added to an ink in the writing instrument and the adding amount of which is 0.01 to 10% by weight based on total amount of the ink.
(6) The writing instrument having an excellent cap-off performance as described in any of the above items (1) to (5), wherein the substance providing a cap-off property which is added to the ink is at least one selected from glycerin derivatives, alkylphosphoric acid esters, polyoxyethylenesorbitan fatty acid esters, polyoxyethylenesorbit fatty acid esters, paraffin wax, microcrystalline wax, polyolefin wax, pentaerythritol derivatives and lecithin.
(8) The writing instrument having an excellent cap-off performance as described in any of the above items (1) to (6), being a direct liquid writing instrument comprising an ink tank part which is a barrel for directly storing an ink and a collector member for temporarily reserving the ink, wherein the ink is derived from the ink tank part to the pen tip directly or via a feed.
(9) The writing instrument having an excellent cap-off performance as described in any of the above items (1) to (6), being a writing instrument having an ink reservoir absorbing an ink in a barrel, wherein the ink is derived from the ink reservoir to the pen tip directly or via a feed.